The present invention relates in general to muscle relaxation, and more particular to muscle relaxation for spastic muscles in patients having injuries to the central nervous system (CNS) at least by using muscle stimulation.
Injuries to the central nervous system (CNS) are difficult to treat and cure. Spastic paresis, which is a pathologically increased muscle tonus caused by an injury to the central nervous system (CNS) is a significant obstacle for prevention of posturing and loss of mobility.
Today, therapeutic alternatives for the reversal of CNS injury symptoms, such as spasticity, are very limited. Therapies are constructed to prevent further loss of function, rather than alleviating the symptoms. No treatment has been found to truly give back function and, in the long run, reversing the injury through muscle relaxation of spastic muscles.
In addition to the spasms themselves, musculoskeletal pain is a common related complaint. Pain originating from dysfunction in the musculoskeletal system is in most cases caused by muscle spasms due to muscular imbalance. If the pain is not treated properly, patients risk developing chronic pain syndromes, conditions that are difficult to cure.
There are several techniques available to affect muscles in the human body. Electrical muscle stimulation (EMS), also known as neuromuscular electrical stimulation or electromyostimulation is a commonly known method for increasing muscle mass in specific areas, by providing an electric current into the muscle causing contraction, which gradually leads to increased mass in the treated muscle.
Trancutaneous Electrical Nerve Stimulation (TENS) is closely related to EMS, but instead of stimulating muscles to contract, electric stimulation is used to indirectly treat pain, by distracting the brain through the stimulation of other body parts. In U.S. Pat. No. 4,580,572, a garment for electrical monitoring of sites or electrical stimulation, such as EMS is disclosed.
However, none of the currently known muscle stimulation techniques is suited to provide for targeted muscle relaxation. Hence, a new arrangement including a garment allowing for increased muscle relaxation would be advantageous.
In general, the parameters of the EMS current signal may be chosen which resemble the physiology of the body. The signals in the nervous system may be compared to current impulses (stimuli) to the synapses. When a certain amount of stimuli has occurred, signal substances are excreted.
Generally, a phasic EMS-stimulus is given with a frequency ranging between 2 and 50 Hz, and having a duration between 5 to 300 microseconds.
Muscle relaxation in spastic muscles gives the possibility to induce controlled functional muscle contraction in chosen relaxed muscles. The frequency needed to induce muscle contraction is higher than the frequency used for optimal antagonist muscle relaxation (20 Hz/30 μs). Stimulation frequencies for functional muscle contraction are ranging from 25 to 50 Hz and the duration needed is between 50-300 μs.
The pulsed EMS current signal is controlled by at least the following parameters; pulse frequency, pulse duration, pulse strength.
Experiments have shown that muscles start to contract at a pulse frequency of approximately 15 Hz to approximately 35 Hz, at which frequency range the central nervous system feels the presence of the current signal. The present inventor has realized that by choosing a frequency as low as possible, but still detectable by the central nervous system, the discomfort for the patient is reduced, while the automatic relaxation of the spastic antagonist muscle is taken care of by the central nervous system. A higher frequency than approximately 35 Hz would lead to shortening of the stimulated agonist muscle and therefore activation of the stretch reflex in the antagonist muscle which is not desired, since this would lead to a reciprocal spasm of the agonist muscle.
The pulse duration of the current signal is selected such that it resembles the pulse duration of nervous signals. For example, a pulse duration of approximately 5 to 60 microseconds, such as 30 μs, has been found to be suitable. However, even shorter pulse duration could be advantageous. Too long pulse duration of the EMS current signal does not correspond to the neurophysiologic parameters of the body.
Furthermore, longer pulse duration may also increase the risk of muscle shortage, which is not desired.
Since the spastic muscle behavior in CNS injured patients differs greatly, the professional skills of a neuromuscular system specialist is required for calibrating the system before use, such that the correct agonist muscles are provided with EMS electrodes and joints corresponding thereto are provided with vibrator devices. Every chosen muscle stimulation is paired with an anatomically relevant joint stimulation in order to strengthen the desired relaxation effect. Furthermore, the parameters of the pulsed EMS current signal need to be selected, which parameters may differ between patients.
The above-described stimulation and calibration techniques are further disclosed in WO-2011/067327, which relates to a system and garment for muscle relaxation of a spastic muscle, and is assigned to the applicant of the present application. In particular the system is adapted to cause muscle relaxation by reducing muscular spasticity through stimulation of joints and muscles. The system consists of a garment with electrodes, a hardware unit and software controlling the stimulation.
WO-03/006106 relates to a method and apparatus for electrical stimulation to selected tissues via an array of electrodes positioned on and/or in the body. Each electrode may be connected either as anode, cathode or neither to provide discrimination between stimulated and non-stimulated regions of tissues of the body.
WO-2011/079866 relates to an apparatus for external activation of paralyzed body parts by stimulation of peripheral nerves.
US-2011/0152968 relates to an orthosis for a gait modulation system, and finally, U.S. Pat. No. 7,072,721, that relates to an electrode vest for electrical stimulation of the abdomen and back
Today, when performing external electrical stimulation therapy, it is common to use electrode patches provided with an adhesive for attaching the electrodes to the patient's skin. These electrode patches are disposable, and it is often very time-consuming to attach the electrodes and to connect the electrical cables to each of the electrode patches.
The object of the present invention is to achieve an improved stimulation therapy arrangement, which is more user-friendly and less time-consuming to use, than the presently used adhesive electrodes.
As an electrical stimulation therapy preferably must be applied at least 30 minutes in order to give prolonged effect, one further and important aspect of the stimulation therapy arrangement is that it is comfortable and easy to use for the wearer.